PAIRED TONE FACILITATION IN DORSAL COCHLEAR NUCLEUS NEURONS - A SHORT-TERM POTENTIATION MODEL TESTABLE IN-VIVO

It has been suggested that the dorsal cochlear nucleus (DCN) is involv ed in coding stimulus history or prior auditory activity [Manis (1989) J. Neurophys, 61, 149-161; Manis (1990) J. Neurosci., 10, 2338-2351]. The major output neurons of the DCN are the fusiform (pyramidal) cell s which are thought to receive excitatory inputs from the descending b ranch of the acoustic nerve onto their basal dendrites and significant inhibitory glycinergic and GABAergic inputs to the soma and dendrites . The apical dendrites of these neurons lie within the molecular layer of the DCN and encounter parallel fibers which are thought to utilize the excitatory amino acid neurotransmitter glutamate. In this study o f anesthetized chinchillas, we found that, in contrast to the response s of acoustic nerve fibers and most cochlear nucleus neurons which are masked by an appropriate preceding signal, many DCN principal cells a re facilitated during the second of two identical stimuli. Facilitated DCN responses often have a reduced interspike interval and a more cho pper-like temporal response pattern to the second characteristic frequ ency tone. This paired tone facilitation in the chinchilla DCN provide s an in vivo model of short-term potentiation elicited by sensory stim ulation similar to the paired-pulse facilitation observed with electri cal stimulation in other models.